This 2005 photo shows the Blackleaf area of the Rocky Mountain Front south of Glacier National Park, in Montana. There are about two dozen glaciers that remain at the picturesque park, but most are located in the backcountry where visitors never see them.

Imagine the Grand Canyon – so achingly vast and vacant – filled to the rim with the daily din of machinery, like the background hum a big city.

Envision no more glaciers at Montana’s Glacier National Park, where since 1979 the average temperature has nudged two degrees higher.

Following a pair of recent studies that exposed man-made and climate-caused deterioration at those two iconic American attractions, environmentalists are raising new concerns about the future health of all 58 U.S. national parks in a time marked by barren budgets, rising energy cravings and warming skies.

At Saguaro National Park in Arizona, the very species that gave the refuge its name – the tree-sized, saguaro cactus – is imperiled by an invasive, fire-prone, African weed first introduced to U.S. soil 80 years ago as livestock forage. On private land outside Utah’s Bryce Canyon National Park, a coal company has been cleared to launch a 440-acre strip mine that, ecologists say, could pollute waterways and send dust clouds over the park. At Great Smoky Mountains National Park in Tennessee and North Carolina, a centuries-old canopy of hemlock trees is being eaten away by the woolly adelgid, an Asian insect first spotted in the park in 2002 – probably carried in unknowingly by a tourist, according to one park expert.

With teams using more than 100 unique apparatuses to launch globular projectiles a half-mile or more, the 27th annual World Championship Punkin Chunkin event is our pick as November’s Weird Festival of the Month.

“So we have these threats,” said David Nimkin, southwest regional director of the National Parks Conservation Association, the agency that last week released a status report on the Grand Canyon. “I think sometimes there is a level of complacency where we tend to think of our national parks as already being protected.”

But beyond climate change, and beyond mining and drilling projects on the fringes of other national parks, one of the most pressing dangers to these precious places is the people who most adore them.

The unnatural footprint left by hundreds of millions of park visitors is growing, environmentalists say. Hikers wander off marked trails, trampling vegetation. Vehicles clog park roads and sully the air with tailpipe emissions. Tourists leave behind water bottles and other scraps of litter. Above many national parks, sightseeing planes and helicopters buzz.

“We really count on the visitor having a sense of ownership of national parks,” said Jeffrey G. Olson, a public affairs officer with the National Park Service. “We remind them [the] parks are here for them to enjoy and ask they help make sure they are here for future generations, too.”

But the conga lines of tourists and cars are getting longer. As the U.S. economy turned sour, park visits rose. In 2009, 285 million people spent a collective 1.25 billion hours inside the national parks, the highest numbers since 2000, according to NPS figures.

“Traffic hassles in a national park, you ask?” Olson said. “Here’s one: finding a parking spot at the Logan Pass Visitors Center in Glacier National Park.”

“I don’t want to say the future is bleak” for the parks, given the man-made degradation, said Nimkin. “I mean, we can do something about it.” One change he hopes to see is a federally-mandated cap on the number of air tours over the Grand Canyon, no-flight “respite” periods during certain months, and a relocation of flight routes away from some rim edges and other popular hiking and backpacking spots. An increase in sightseeing flights could eventually fill the canyon with the “background drone we have in our cities,” Nimkin said.

“Think about your time in a special place: it’s the sound of the loon on the lake; it’s the sound of the wind in the trees,” he said. “The full richness of the experience is so profoundly enhanced by that sense.”

When the NPS was created in 1916 to oversee the parks, the understanding was the federal agency would maintain and protect those sanctuaries, Nimkin added. “They would be places that our children and grandchildren would enjoy, and I think we need to uphold that bargain.”

At NPS, Olson said rangers (and signs) have long urged visitors to stay on the marked trails and to park in designated areas and ride shuttles through the parks. At Glacier, Grand Canyon and Zion national parks, bus systems now “help ease traffic congestion, reduce greenhouse gas emissions and make a park visit more fun and relaxing.

But several frequent park users said environmental groups must remember that the national parks are meant to be hiked, driven and rafted or absorbed from above, that they were specially designated as places to be seen, felt and touched by people. And some – or perhaps much – of the deterioration of the park landscapes is simply due to our planet’s normal aging, some of those users maintain.

“I do believe that part of this is ... just natural decay. The earth does break down after a while,” said Ken Donaldson, a life coach and mental health counselor in Tampa, Fla., who spent much of his childhood – and now his adulthood – walking through more than 20 national parks. “What do we do, stop people from coming?” He suggests that “perhaps a scheduling system might create better management” of the parks, and he advocates a cap on the number of daily visitors.

There’s no question that “much of the pressure felt by our national parks originates from beyond park borders,” said Steven Silberberg, a Hull, Mass.-based backpacker who has visited at least six national parks, including Yosemite. “For example, ranchers kill bison all the time just outside the borders of Yellowstone National park for fear that their cattle will contact brucellosis. They also kill wolves and bears because they fear losing cattle ...

“Ultimately, I think one problem is that we expect the national parks to be static museum exhibits, when they are ever-changing dynamic landscapes subject to the same forces that the rest of the world experiences, from erosion to global warming to tectonic activity,” added Silberberg, owner and operator of Fitpacking, a company that guides people on backpacking adventure vacations to help them get in shape.

Texas rancher and artist Pablo Solomon – a self-described environmentalist since the first Earth Day in 1970 – suggests the parks adopt “defined use areas” for various crowds. “Some for tourists, some for serious hikers, some to just drive or ride the tram through,” he said. “The most popular and accessible parks are over run. [But] there are solutions.”

Above Great Smoky Mountains National Park, Dan Haynes believes he’s at the forefront of one of those solutions: he owns and operates Scenic Helicopter Tours, which is based in Sevierville, Tenn. The Air Tour Management Act of 2000, he said, already limits him to 1,800 sightseeing flights annually.

“As for the impact of air tours over the parks, I believe [they have] the least negative impact [on] the environment – but the worst perceived impact by those enjoying the parks from the ground,” Haynes said “Helicopters are generally 1,000 feet or higher above the ground and fly at speeds above 100 miles per hour. They leave no footprints, no trash and offer many people a fantastic view ... In short, we are not around long and we leave no trace.

“I’ve never been to the Grand Canyon,” Haynes added. “But wasn’t it created by erosion? Sorry, I just had to mention that.”

Video: Park rangers to tourists: Put gadgets away

Transcript of: Park rangers to tourists: Put gadgets away

MATT LAUER, co-host:If you're headed to a
national park
before
the end of summer
, you're going to have a lot of company.
Yellowstone
, for example, is playing host to record crowds.

ANN CURRY, co-host:And those visitors are toting more technology than ever,
digital cameras
,
smart phones
,
GPS
locators. But as
NBC
's
George Lewis
found out, all those gizmos can sometimes lead to trouble.

Mr. KEN PHILLIPS:Did you see a deer?

GEORGE LEWIS reporting:Park rangerKen Phillips
runs
emergency services
at the
Grand Canyon
. His mission is to keep park visitors safe, and there are plenty of those.

Ms. SHANNAN MARCAK (Grand Canyon National Park Spokesperson):On average, we've been doing about four and a half million visitors each year.

LEWIS:And these days, those visitors come laden with technology. The young woman from
France
with her
iPhone
, the guy from
Japan
balancing video and still cameras, and plenty of Americans eager to share their pictures with folks back home. Here's the old
point of view shot
over the
canyon rim
as we come
close to the edge
. But while people are carrying
smart phones
, they're not always doing smart things. I can use
GPS
to find out where I am at all times, and if I get so absorbed in this gadget that I forget the basics of safety, I can get in a lot of trouble. Just ask
Kathy Hayes
, whose brother-in-law
Donald
spotted a bison in
Yellowstone
.
Kathy
, sensing the perfect
YouTube
moment, followed, camera rolling.

Ms. KATHY HAYES:We'll get a shot of
Donald
getting gored by the buffalo.

LEWIS:But when the bison got angry and charged, it was
Kathy
, not
Donald
, he went after.

Ms. HAYES:No! It was a traumatic experience. So yeah, just don't do what I did. Be smart, people.

LEWIS:Ken Phillips
says while rescue numbers remain constant, one of his technical pet peeves is a spike in false alarms sent by people with
emergency beacons
like the kind skiers use in avalanches. Here, most of the last dozen alerts have been for trivial problems like bad-tasting water.

Mr. PHILLIPS:There were only two where people really sustained an injury that required an emergency response.

LEWIS:So the message from the rangers: Enjoy the parks, take home lots of digital memories, but just remember the safety rules.

Acadia

Acadia National Park in Maine boasts the highest mountain on the U.S. Atlantic Coast and was the first national park east of the Mississippi River. Visitors beware: temperatures can vary 40 degrees -- from 45 degrees to 85 degrees in the summer and from 30 degrees to 70 degrees in the spring and fall.
(Gareth Mccormack / Lonely Planet Images)
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Rocky Mountain

Bear Lake, with mountainside aspens changing colors in mid-autumn, is one of the popular attractions in Rocky Mountain National Park in Colorado.
(Universal Images Group via Getty Images)
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Badlands

The climate in South Dakota's Badlands National Park is extreme. Temperatures range from minus 40 degrees in the dead of winter to 116 degrees in the height of summer. Visitors are drawn to the park's rugged beauty as well as the area's rich fossil beds.
(Mark Newman / Lonely Planet Images)
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Yosemite

One of the nation's first wilderness parks, Yosemite is known for its waterfalls, scenic valleys, meadows and giant sequoias.
(Robert Galbraith / Reuters)
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Redwood

Created in 1968, Redwood National Park is located in Northern California. Today, visitors to the national park can enjoy the massive trees as well as an array of wildlife.
(David Gotisha / msnbc.com)
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Joshua Tree

Joshua Tree National Park is located in southeast California. The area was made a national monument in 1936 and a national park in 1994. Outdoor enthusiasts can go hiking, mountain biking and rock climbing.
(Gabriel Bouys / AFP - Getty Images)
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Great Smoky Mountains

Straddling the Tennessee-North Carolina border, Great Smoky Mountains National Park encompasses more than 800 square miles in the southern Appalachian Mountains. Visitors can expect mild winters and hot, humid summers, though temperatures can differ drastically as the park's elevation ranges from 800 feet to more than 6,600 feet.
(AP)
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Arches

More than 2,000 natural sandstone arches, many of them recognizable worldwide, are preserved in Utah's Arches National Park. Temperatures can reach triple digits in the summer and can drop to below freezing in the winter.
(AP)
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Grand Teton

The Snake River flows through Grand Teton National Park, and the jagged Teton Range rises above the sage-covered valley floor. Daytime temperatures during summer months are frequently in the 70s and 80s, and afternoon thunderstorms are common.
(Anthony P. Bolante / Reuters)
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Haleakala

Visitors watch the sun rise at 10,000 feet in Haleakala National Park in Maui, Hawaii. If weather permits, visitors at the top of the mountain can see three other Hawaiian islands.
(The Washington Post via Getty Images)
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Grand Canyon

Grand Canyon National Park is perhaps the most recognizable national park. Nearly 5 million visitors view the mile-deep gorge every year, formed in part by erosion from the Colorado River. The North and South rims are separated by a 10-mile-wide canyon.
(Gabriel Bouys / AFP - Getty Images)
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Yellowstone

Yellowstone National Park, America's first national park, was established in 1872. The park spans parts of Wyoming, Montana and Idaho. Grizzly bears, wolves, bison and elk live in the park. It is well known for Old Faithful and other geothermal features.
(Mark Ralston / AFP - Getty Images)
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Hawaii Volcanoes

Two of the world's most active volcanoes can be found within Hawaii Volcanoes National Park. In 1980, the national park was designated an International Biosphere Reserve; in 1987, it was added as a World Heritage Site.
(David Jordan / AP)
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Everglades

Everglades National Park covers the nation's largest subtropical wilderness. It is also a World Heritage Site, an International Biosphere Reserve and a Wetland of International Importance. Visitors to the park can camp, boat, hike and find many other ways to enjoy the outdoors.
(Joe Raedle / Getty Images)
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Glacier

A view from atop the Grinnell Glacier Overlook trail in Glacier National Park. With more than 700 miles of trails the park is known for its glaciers, forests, alpine meadows and beautiful lakes.
(Matt McKnight / Reuters)
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Bryce Canyon

Located in southwestern Utah, Bryce Canyon National Park is known for its distinctive geological structures called "hoodoos."
(Mark Ralston / AFP - Getty Images)
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Crater Lake

The brilliant blue Crater Lake, located in southern Oregon, was formed when Mount Mazama, standing at 12,000 feet, collapsed 7,700 years ago after a massive eruption. Crater Lake is one of the world's deepest lakes at 1,943 feet.
(David Gotisha / msnbc.com)
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Olympic

Washington state's Olympic National Park offers visitors beaches on the Pacific Ocean, glacier-capped mountain peaks and everything in between. Keep the weather in mind when visiting, though, as roads and facilities can be affected by wind, rain and snow any time of year.
(National Park Service)
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Sequoia and Kings Canyon

A woman stands among a grove of a Giant Sequoia trees in Sequoia National Park in Central California. The trees, which are native to California's Sierra Nevada Mountains, are the world's largest by volume, reaching heights of 275 feet and a ground level girth of 109 feet. The oldest known Giant Sequoia based on its ring count is 3,500 years old.
(Mark Ralston / AFP - Getty Images)
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Kenai Fjords National Park

The National Park Service considers the 8.2-mile round-trip on Harding Icefield Trail in Alaska's Kenai Fjords National Park to be strenuous, saying hikers gain about 1,000 feet of elevation with each mile.
(National Park Service via AP)
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Death Valley

California's Death Valley encompasses more than 3.3 million acres of desert wilderness. In 1849, a group of gold rush pioneers entered the Valley, thinking it was a shortcut to California. After barely surviving the trek across the area, they named the spot "Death Valley." In the 1880s, native peoples were pushed out by mining companies who sought the riches of gold, silver, and borax.
(Gabriel Bouys / AFP - Getty Images)
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Wind Cave

Bison graze in Wind Cave National Park in the southern Black Hills of South Dakota. Millions of bison were slaughtered by white hunters who pushed them to near-extinction by the late 1800s. Recovery programs have brought the bison numbers up to nearly 250,000.
(David McNew / Getty Images)
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Canyonlands

The Lower Basins Zone is outlined by the white rim edge as seen from the White Rim Trail in Canyonlands National Park, Utah.
(Doug Pensinger / Getty Images)
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